I went to T25-base 20k starting stacks with antes for our league play many years ago. Two tables of eight with a single re-buy option, 50/100 opening blinds for 200bb. Finishes in under 5 hours.
We are experimenting a bit this year, adding two other tourney structures into the mix: T100-base 30k stacks with a bba (no rebuys, same blinds as the 20k above but starting at 100/100, 300bb), and T25-base 25k stacks with re-buy but no antes, using a more aggressive blind structure (50/100, 250bb).
The current league season consists of 9 events, 3 of each type (20k w/antes, 25k no-antes, 30k w/bba).
I haven't organized a 10k event in years, and have no plans for ever going back.